# include<stdio.h>
# include<stdlib.h>
# include<string.h>

int main()
{
    // 利用getenv这个系统调用来获取环境变量
    char* who = getenv("USER");
    if(strcmp(who, "root") == 0)
    {
        printf("user:%s\n", who);
    }
    else
    {
        printf("Permission denied\n");
    }

    return 0;
}
